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排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The aim of this paper is to study a multiplier family of harmonic univalent functions using the sequences {cn} and {dn} of positive real numbers. By specializing {cn} and {dn}, the generalized Bernardi–Libera–Livingston integral operator is modified for such functions and the closure of the multiplier family under the modified integral operator is determined. Also, convolution products, closure properties, distortion theorems, convex combinations and neighborhoods for such functions are given. 相似文献
992.
Songxiao Li 《Applied mathematics and computation》2009,214(1):304-309
The boundedness of the generalized Hilbert operator on the Dirichlet-type space Sp when 0<p<1 is investigated. 相似文献
993.
本文研究了完备布尔代数L的商格Q(L),建立 L上q-集构成的集合Q′(L)与Q(L)之间的同构,得出了完备布尔代数的商格仍是完备布尔代数,并给出了完备布尔代数范畴的某些性质. 相似文献
994.
995.
In this work, we study the stability of the solution semigroup for some linear partial functional differential equations with infinite delay in a Banach space when the exponential stability fails. We use the so-called characteristic equation to compute the order of each pole of the resolvent operator associated with the infinitesimal generator of the solution semigroup. This result allows us to give sufficient conditions for having stability of the solution semigroup. 相似文献
996.
In this paper we study asymptotic properties of the third order trinomial delay differential equation (*) y‴(t) − p(t)y′(t) + g(t)y(τ(t)) = 0 by transforming this equation to the binomial canonical equation. The results obtained essentially improve known results
in the literature. On the other hand, the set of comparison principles obtained permits to extend immediately asymptotic criteria
from ordinary to delay equations.
Research was supported by S.G.A. No.1/003/09. 相似文献
997.
S. V. Astashkin D. V. Zanin E. M. Semenov F. A. Sukochev 《Functional Analysis and Its Applications》2009,43(2):83-95
The Kruglov property and the Kruglov operator play an important role in the study of geometric properties of r. i. function spaces. We prove that the boundedness of the Kruglov operator in an r. i. space is equivalent to the uniform boundedness on this space of a sequence of operators defined by random permutations. It is also shown that there is no minimal r. i. space with the Kruglov property. 相似文献
998.
Javier Parcet 《Journal of Functional Analysis》2009,256(2):509-593
The weak type (1,1) boundedness of singular integrals acting on matrix-valued functions has remained open since the 1980s, mainly because the methods provided by the vector-valued theory are not strong enough. In fact, we can also consider the action of generalized Calderón-Zygmund operators on functions taking values in any other von Neumann algebra. Our main tools for its solution are two. First, the lack of some classical inequalities in the noncommutative setting forces to have a deeper knowledge of how fast a singular integral decreases—L2 sense—outside of the support of the function on which it acts. This gives rise to a pseudo-localization principle which is of independent interest, even in the classical theory. Second, we construct a noncommutative form of Calderón-Zygmund decomposition by means of the recent theory of noncommutative martingales. This is a corner stone in the theory. As application, we obtain the sharp asymptotic behavior of the constants for the strong Lp inequalities, also unknown up to now. Our methods settle some basics for a systematic study of a noncommutative Calderón-Zygmund theory. 相似文献
999.
Christiane Tretter 《Journal of Functional Analysis》2009,256(11):3806-3829
In this paper we establish a new analytic enclosure for the spectrum of unbounded linear operators A admitting a block operator matrix representation. For diagonally dominant and off-diagonally dominant block operator matrices, we show that the recently introduced quadratic numerical range W2(A) contains the eigenvalues of A and that the approximate point spectrum of A is contained in the closure of W2(A). This provides a new method to enclose the spectrum of unbounded block operator matrices by means of the non-convex set W2(A). Several examples illustrate that this spectral inclusion may be considerably tighter than the one by the usual numerical range or by perturbation theorems, both in the non-self-adjoint case and in the self-adjoint case. Applications to Dirac operators and to two-channel Hamiltonians are given. 相似文献
1000.
Dragan Juki 《Journal of Approximation Theory》2009,156(2):212-222
For the given data (wi,xi,yi), i=1,…,M, we consider the problem of existence of the best discrete approximation in lp norm (1≤p<∞) by reciprocals of real polynomials. For this problem, the existence of best approximations is not always guaranteed. In this paper, we give a condition on data which is necessary and sufficient for the existence of the best approximation in lp norm. This condition is theoretical in nature. We apply it to obtain several other existence theorems very useful in practice. Some illustrative examples are also included. 相似文献